Oil well inhibitor



01L WELL INHI I-Ion DArcyA. Shock and Warren W. Woods, Ponca City, Okla., assignors to Continental Oil Company, Ponca City, Okla., a corporation ofDelaware No Drawing. Application May 14, 1956 Serial No. 584,445

7 Claims. (Cl. 252-8'.55)

This invention relates to the prevention of corrosion of metal equipment in producing'oil wells and is a continuation-in-part of our copending application, Serial No. 393,962, filed November 23*, 1953, now abandoned. More particularly; the invention relates to the protection of steel casings, steel tubing, and other metal well equipment from the deleterious effects of corrosive formation liquids.

-In the production of oil, corrosion of steel and other metal well equipment is caused by the action of certain types of sulfur-bearing waters, aqueous carbonic acid, and natural brines. Corrosive: sulfide brines include alkali and alkaline earth metal sulfides and hydrogen sulfide. Hydrogen sulfide is very soluble in water, brines, and crude oil forming corrosive solutions which cause deterioration of well and surface equipment. This corrosion United States Patcnt takes place in both acidic and alkaline brines having a pH below about 8, which includes practically all natural well.- brines.

It is common practice to introduce an inhibitor at the well head into the. annular space between the casing and the tubing in a, well extending into a producing formation. The liquid inhibitors which have been used are expected to flow to at producing zone in the well, to mix with the corrosive liquids flowing therefrom, and thusflow' up through the tubing tothe. surface.

In gas lift wells. in particular and in some. pumping and flowing wells, a considerable column. of oil and water or brine may stand in the annular space bet-ween casing and producing tubing. In such wells the conventional inhibitors will be rather ineffective in extending protection from corrosion throughout the well. We have found that two additional requirements must be met to insure eflective utilization of the inhibitor. First, the density of the inhibitor must be greater than that of the liquids contained in the well, and second it must not be appreciably soluble in crude. oil.

it is a principal Object of this invention, therefore, to provide a method of in ibiting; corrosion in producing oil wellsv in which the corrosion inhibitor is weighted with a dispersed. solid to enable it to fall more'readily through. any liquid column in the well to a producing zone therein.

A further object of the invention is to render oil-soluble inhibitors suffi'ciently limited in solubility so as to pass readily through an oil layer floating upon a column of brine without appreciable dissolution by providing a dispersed solubility-limiting weighting solid in combination .with a corrosion inhibitor.

after fully described and particularly pointed out in theclaims, the following description setting forth in detail pertain. illustrative emhodimcntsof. the; invention, these.

2,853,452 Patented Sept. 23, 8

2 being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.

We have found that inorganic solids, preferably the alkaline or basic inorganic compounds, can be combined in a finely dispersed solid state with the normally liquid iron corrosion inhibitors to produce compositions, having increased density and reduced oil solubility. Such weighted inhibitor compositions have been prepared which are not detrimental to the operation of the well, and when the preferred basic solids are used, the effective ness of the inhibitor is actually enhanced by a buffering action of such solids therewith} Moreover, in some instances, the weighted compositions of this invention have the added property-of acting as sequestering agents for preventing a natural deposition of mineraldepo sits such as carbonates within a well.

Broadly stated, our invention comprises the method of inhibiting corrosion in oil wells consisting in weighting an inhibitor with an inorganic solid dispersed therein to provide a composition which when added at the wellhead will drop readily through any bore-standing oil and aqueous column, diffusing in part with the aqueous phase, and arrive in substantial quantity at a producing zone or well bottom to cornmingle with liquids produced therefrom. The Weighted inhibitor compositions of this invention may be describedbroadly as a two-phase system consisting of a dispersed solid phase and a continuous normally liquid phase. The liquid phase consists primarily of the corrosion inhibitonbut may also include a carrier such as mineral oil. This continuous liquid phase may in some instances also contain other material, the specific function of which is to act as a dispersant or stabilizing" agent for the inorganic solid. The disperse phase consists of a finely divided inorganic solidwhich is stably suspended in the liquid phase; the inorganic solid is'preferablyan alkaline or basic compound consisting of, an inorganic alkali or alkaline earth-metal salt which is soluble in either water or a lower molecular weight aliphatic alcohol- There are two methods which are particularly effective for the purposes of the present invention for forming stable dispersions of inorganic solids-in-oil wherein the diameter of the individual particles of the inorganic solid is less than 1 micron. One such method is that disclosed by the present co-inventor Woods in his co-pending application, Serial No. 297,777, filed July 8, 1952. Another method is that disclosed by Carlyle in the co-pending application Serial No, 362,970, filed June 19,, 1953, now abandoned. Both applications are assigned to the present assignee and both disclosures are hereby made a part of this application. Briefly the former application discloses a method of-forming a stable oil dispersion. of a basic water-solubl inorganic compound by first dissolving the, inorganic solid compound in water at concentrations ranging up to saturation, emulsifying this aqueous solution in an oil containing as a dispersing agent an organic acidwhose normal alkali and alkaline, earth metal salts are oil soluble, or an organic compound which, upon hydrolysis, yields such an acid, forming a finely divided water-in-oil emulsion, and then dehydrating the emulsion. As a specific example disclosing the preparation of such a stable dispersion in oil the following is given: .One hundred grams of borax were dissolved in 400 grams of water. A solution consisting of grams of 170 S. S. U. (Saybolt viscosity seconds universal at F.) Mid- Continent pale oil and 75' grams of phosphorus penta- 3 fine water-in-oil emulsion. Heating of the emulsion was continued at a temperature of 98 -100 C. to eliminate the water, leaving an extremely fine suspension of borax in oil. Heating the concentrate, with stirring was continued to 130 C. to remove the water completely. The resulting dehydrated concentrated dispersion was optically clear to transmitted light. The Carlyle application teaches a method of dispersingsolid basic inorganic salts in an oily phase by means of volatile organic solvents, the process of which may be described as comprising the steps of admixing at least one basically reacting inorganic metal compound, an organic acid compound of the type whose barium salts of the anion are oil soluble, mutual solvents for these compounds, and water to form a homogeneous mass, and subsequently removing the mutual solvents and water therefrom. As a specific example disclosing the preparation of such a stable dispersion in oil the following is given: A methanolic solution of barium oxide was prepared by dissolving 88 parts by weight of barium oxide in 352 parts by weight of methyl alcohol. This solution after filtration had a base number of 122. 70.5 parts by weight of a diwaxbenzene sulfonic acid (2.50 milliequivalents/gram), 202.7 parts by weight of 170 pale oil, 960.4 parts by weight of benzene, and 26.4 parts by weight of water were added to a Pfaudler reaction vessel. Two hundred parts by volume of the methanolic barium oxide solution was then slowly added while the mixture was stirred and heated to about 60 C. which caused the evaporation of the methanol-benzene azeotrope causing the precipitation of the barium oxide as a finely divided material. At this point an additional 440.5 parts by weight of benzene was added. The temperature was then gradually raised to 150 C. to remove all of the solvents, the water, and the excess benzene. The resulting product was bright, analyzed 17.4 percent barium and 1.8 percent sulfur. As above used, the descriptive terms for the dispersing agent, organic acid and organic acid compounds," are meant for the purposes of this invention to include the oil soluble free acids and salts thereof as well as organic compounds which, upon neutral or alkaline hydrolysis, yield oil soluble acids or salts. For the production of the weighted inhibitor compositions, it will be shown hereinafter that the above-described dispersing agents, disclosed in the cited Woods and Carlyle applications, include members which also possess corrosion inhibiting properties. These dispersant-inhibitors will supplement the general group of corrosion inhibitors to be weighted in accordance with our invention.

Whichever method of preparing the solid-in-oil dispersion is used, an amount of the solid must be employed to produce an inhibitor composition having a specific gravity sufiicient to enable the weighted composition to fall readily through a column of crude oil and aqueous liquids generally found in oil wells. The actual density of the solid that should be used is dependent upon two variables. One, the concentration of the solid which may be used in the corrosion inhibiting composition and, two, the density of the brine column in the well. As to the latter, that varies with different wells. For example, the densities of brine solutions from wells located in South Texas and Ceres Pool Field may run as high as about 1.05 and 1.18, respectively. It therefore follows that if the inhibiting solution is to be used in South Texas a density of about 1.06 would be suflicient while an inhibiting solution having a density of about 1.2 may be required if it is to be used in the Ceres Pool Field. The foregoing values are maximum and as a rule an inhibiting composition the density of which is greater than 1.01 will be suitable for use in many wells. Generally we prefer to use an amount of solid which will produce a specific gravity of at least about 1.05. Obviously the concentration of the dispersed solids required for weight-, ing the inhibiting composition is dependent upon the respective densities of each of the components employed in w the finished weighted composition. Since the densities of the iron corrosion inhibitor and the oil are less than one,

on a weight basis the solids content of the composition must be about 10 percent if the density of that solid is about 6. Likewise if the density of the solid is only 1.5 about 40 percent of the solid must be used to accomplish the same result; namely, produce an inhibiting composition having a density of 1.05.

Either of two approaches may be taken for the preparation of the weighted inhibitor. The first would be to prepare a dispersion of the solid in oil with an organic dispersant of the class above described (i. e., a substance not necessarily possessing corrosion inhibiting properties),

and to this dispersion then admix a corrosion inhibiting compound. The second approach would be to disperse the solid directly into an inhibitor composition, itself acting to stabilize the dispersion and which may also contain mineral oil and/or an additional amount of a dispersing agent selected from that class of dispersing agents hereinbefore described in order to stabilize the product if such stabilization is necessary. 1

Various known iron corrosion inhibitors may be employed in producing the weighted compositions of this invention. These include the nitrogen type of inhibitors, the salts of petroleum and other organic sulfonic acids, and the like. An example of the nitrogen-based inhibitor is a primary high molecular weight amine derived from rosin by reacting rosin with ammonia after which the resulting product is hydrogenated to form the amine. Other amines prepared from modified (hydrogenated and dehydrogenated) rosins are likewise useful. Such products are available from Hercules Powder Company under the trade name Rosin Amine. A group of useful inhibitors are the quaternary ammonium salts such as the dialkyl dimethyl ammonium chlorides in which the alkyl groups contain from 8 to 18 carbon atoms. One such material is manufactured by the Chemical Division of Armour and Company and. sold under the trade name Arquad 2C. Still another useful nitrogen type inhibitor is a condensation product of oleic acid and aminoethylethanolamine available as Amine 220 from Car bide and Carbon Chemicals Company. The nitrogen ring inhibitors include acridine and derivatives, pyrrole and derivatives, and morpholine and derivatives.

The sulfonates which are useful as inhibitors in the practice of this invention include the salts of the so-called mahogany or oil-soluble petroleum sulfonic acids. Of the mahogany sulfonates, the oil-soluble salts of the aromatic sulfonic acids from petroleum are particularly effective, and include those having cycloalkyl (i. e., naphthenic) groups attached to the benzene ring. The mahogany acids also include non-aromatic sulfonic acids produced in conventional sulfuric acid refining of lubricating oil distillates and from the industrial use of fuming sulfuric acid in the manufacture of petrolatum. The industrial production of oil-soluble mahogany sulfonates from petroleum is well understood in the art and is described elsewhere in the literature. Among the synthesized organic sulfonates, sulfonated alkaryl compounds such as sodium and calcium polydodecylbenzene sulfonates are very useful corrosion inhibitors in the compositions of this invention.

The polydodecylbenzene sulfonates are prepared by neutralizing polydodecylbenzene sulfonic acid with an appropriate base. Polydodecylbenzene sulfonic acid is prepared by sulfonating polydodecylbenzene, a product consisting of mono-alkyl benzenes and di-alltyl benzenes in the approximate ratio of 2:3. Typical physical properties of polydodecylbenzene are as follows:

Specific gravity at 38 C 0.8649 Average molecular weight 385 Percent sulfonatable Q 88 A. S. T. M., .D-lSS Engler:

I. B. P F; 6.47

The inorganic solids which may be used to make up the weighted inhibitor compositions of this invention include all water-soluble andthe lower alcohol soluble inorganic solid compounds having a density from about 1.4 to about 6 the upper value being a practical limit, the aqueous solutions of which have a. pH preferably of at least 8 and includes the inorganic bases and salts of these bases with weak acids both inorganic and the volatile organic acids. Such compounds include, by way of example, sodium tetraborate (borax); sodium silicate (water glass); lithium, sodium, potassium, and barium hydroxides; basic alkali metal phosphates; alkali metal carbonates, thiocarbonates, and bicarbonates; potassium borates; sodium and potassium aluminates; lithium, sodium, and potassium molybdates; sodium and potassium tellurites; potassium tellurate; ammonium carbonate; and the like metal formates, acetates, oxalates, tartrates, These solids may be dispersed in thecorrosion inhibitor in amounts up to 40 percent by weight or more.

The dispersing agents which may be employed in the practice of the present invention are those. generally disclosed in the above cited co-pending Woods, and Carlyle applications. compounds which include: alkyl phosphorus and thiophosphorus acids, alkyl phenols, naphthenic acids, phosphorus sulfide treated wax olefins, the KOH treated prodnet of polyisobutylene reacted with P 8 the higher aliphatic monoand di-carboxylic acids; aliphatic and aromatic sulfonic acids; and the alkaliand alkaline earthmetal salts of the foregoing organic acids. For oil solubility, the alkyl substituents or groupings of the foregoing acids will contain at least about 14 carbon atoms, and preferably from about l8-24 atoms of carbon. The dispersing agent, usually in admixture with a carrier such as a mineral oil, is usedin an amount such thatv the acid radical thereof will be equivalent to a'combining weight of the metal in the range of 2-20 percent of the amount of the solid substance which isv to be dispersed.

Of the above described dispersing agents, the following types of compounds may also be classed. as corrosion inhibitors for purposes of the present invention. These are particularly the alkaliand alkaline: earth-metal salts and partial esters of: the alkyl phosphorusand thiophosphorus-acids, the higher aliphatic acids, the organic sulfonic acids, and especially the alkyl aromatic sulfonic acids.

For use in a petroleum well, the finished Weighted corrosion inhibiting composition is used in an amount sufficient to maintain an inhibitor concentration of from about 1 to 10,000 p. p. m. of corrosive formation liquids.

Diwax benzene is an article of commerce and may be prepared by a method such as the following: A paraffin wax having an average of 24 carbon atoms to the molecule and a melting point of 126 F. was chlorinated at about 95 C. with chlorine gas until the weight of the wax had increased about 10%. The chlorowax (10% Cl) thus obtained was then blown with nitrogen to remove any occluded chlorine and hydrogen chloride.

Specifically, these are oil-soluble organic One thousand and twenty parts of the above. chlorowax was then reacted with 458 parts by weightv of benzene in the presence of 62 parts of A101 at about 60 C.:for about 2 hours. The excess benzene Was then distilled 01f by warming to 115 C. with a stream of nitrogen gas bubbling through the mixture. The monowax benzene thus formed was treated with an additional .1020 parts of chlorowax and the mixture heated to C. until reaction stopped. It was allowed to stand overnight at about 60 C. and then decanted from the settled AlCl sludge and filtered. The product consisted essentially of diwax benzene. r

The examples; which follow are given to describe the invention further and to illustrate specific applications thereof as outlined in the foregoing description. These examples are illustrative only and many variations will be apparent to those skilled in the art of corrosion and dispersion technique.

The aqueous emulsion method of weightinga corrosion inhibitor with dispersed solids is illustrated as follows.

Example 1 vA dispersion of a water-soluble inorganic solid for use asv avweighting agent was prepared as follows: One hundred and twenty grams of-borax was dissolved in 240 grams of water. Eighty grams of a mineral oildiwaxbenzene sulfonic acid concentrate having an acidity of 0.629 milliequivalent per gram wasv dissolved in 80 grams of 50 S. S. U. (Saybolt Viscosity, sec. at F.) raw Mid-Continent pale oil. This oil solution was placed in a Waring Blender fitted with an immersion heater and heated to- 80 C. The aqueous borax solution was likewise heated and then added to the oil mass in the blender with violent agitation. The result was an extremely fine water-in-oil emulsion. The emulsion was stirred and heated to a temperature of 98100 C. whereupon substantially all of the water was evaporated leaving an extremely finely dispersed solid suspension of borax particles in the oil. Heating this dispersion of solids under continued agitation was carried to a final temperature of 130 C. to insure a substantially anhydrous product. The resultant stable dispersion of borax in oil was mixed with 20 percent of its own weight of a 70 percent active sodium polydodecylbenzene sulfonate to give a weighted inhibitor having a specific gravity of 1.06 enabling it to pass readily through a layer of crude oil without appreciable dissolution and to fall through a brine column, diffusing in part therewith to the producing Zone in a well. The dispersed borax solids serve in a dual role, first to increase the specific gravity of the inhibitor above that of well brines, and second to provide a higher alkalinity for additional corrosion control.

Example 2 Another Weighted inhibitor composition was prepared as follows: One hundred and thirty grams of sodium tripolyphosphate was dissolved in 630 grams of Water. One-third of this solution was emulsified with an oily mixture containing 80 grams of 50 S. S. U. raw pale oil and 80 grams of a mineral oil-diwaxbenzene sulfonic acid concentrate (0.62 meq. acid/gram) in a Waring blenden. The emulsion was formed and dehydrated in the blender while heating to C. to form a solids dispersion of the tribasic phosphate. After cooling below-100C, a second one-third of the aqueous solution was added to the mass in the blender and again emulsified and dehydrated in like manner. Again after cooling, the last one-third of aqueous solution was added, and emulsified and dehydrated as before. This final dispersion product was brought to C. to insure a substantially anhydrous product. Eighty parts of this product was then blended with 20 parts of a 70 percent active sodium polydodecylbenzene sulfonate to give a weighted inhibitor of specific gravity greater than 1.05.

7 The non-aqueous solvent method of weighting a corrosion inhibitor with dispersed solids is illustrated as follows.

Example 3 100 C. The resulting solvent-free dispersion of barium solids was clarified to remove a small amount of settling solids, by diluting with solvent naphtha, centrifuging and evaporating the solvent from the decanted product. The resulting bright appearing inhibitor-solids dispersion has a density of 1.2 and an excess or reserve alkalinity as expressed by a base No. of 80.9 mg. KOH/gram. Thus an inhibitor supplemented by excess alkalinity for additional corrosion control and having a highly increased density is provided for oil well use wherein it will readily penetrate through any bore-standing liquids to reach a producing formation therein for a highly effective distribution for control of corrosion throughout the metal fittings of the well.

Example 4 A solids weighted inhibitor was prepared wherein the inhibitor component was formed from the acidic dispersing agent upon combination with part of the inorganic metal weighting compound, all of which was dispersedthereby. An alcoholic solution containing 17.7 grams of barium oxide and 82.3 grams of methyl alcohol, 15 grams of polydodecylbenzene sulfonic acid, grams of 170 pale oil, and 356 ml; of benzene followed by the addition of 10 grams of water were stirred together forming a homogeneous mass as in the manner of Example 3. The mixture was heated gradually with continued stirring to about 150 C. to progressively distill off the methyl alcohol, benzene, and water. The resulting product was diluted with benzene, centrifuged, and the decanted bright dispersion was heated until free from benzene. The specific gravity of the finished product dispersion was in excess of 1.2, more than ample for use in penetrating to a producing formation through a stand ing column of corrosive well liquids. The product had a base No. of 221 mg. KOH/gram, thus showing an exceptional base reserve for additional corrosion control by combating acidity of the well fluids.

Example 5 The efiiciencies of the corrosion inhibitors prepared according to Examples 1 and 3 were compared by determining the percent protection given a mild steel test coupon subject to corrosion under simulated well conditions in the presence of 250 p. p. m. of inhibitor composition by comparing the weight loss of a similar test coupon when subject to the same corrosion conditions in the absence of the inhibitor composition. A corrosion test cell of about 5 gallons capacity was charged with a 120 pale oil-salt water mixture (concentration of salt in water equal to 30,000 p. p. in.) plus the corrosion inhibitor composition being tested. The oil-salt water mixture was constantly circulated so as to maintain an emulsion, a weighed l-inch by 8-inch l020 mild carbon steel coupon inserted, and the cell stopper fitted on. Carbon dioxide was bubbled through the solution so as to saturate the same. After about 24 hours at a temperature of 140 F. the coupon was removed from the bottle, descaled by scrubbing with a nylon bristle brush and a cleaning powder, weighed and its loss in weight determined.

The same technique was followed to obtain a blank in the absence of corrosion inhibitor. The percent protection was calculated as follows:

P.C.P.= (Wbr Wbf) wh ere P. C. P.=Percent protection attorded by inhibitor.

Wb =lnitial weight of coupon subjected to test in the absence of inhibitor.

Wb =Final weight of coupon subjected to test in the absence of inhibitor.

Wc =lnitial weight of coupon subjected to test in the presence of inhibitor.

li c =Final weight of coupon subjected to test in the presence of inhibitor.

Protection atiorded by the two inhibitor compositions:

It is apparent that many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and the invention is limited only by the terms of the appended claims.

We claim:

1. A method of treating oil wells containing a column of corrosive formation liquids which comprises the addition thereto of a weighted corrosion inhibiting composition, said composition comprising a liquid iron corrosion inhibitor having incorporated therein as a weighting agent a stable dispersion of an inorganic solid in oil wherein the diameter of the individual particles of said inorganic solid is less than 1 micron in an amount suificient to increase the specific gravity of the inhibitor composition above that of the corrosive liquids to enable the inhibitor composition to fall readily through the liquid colume to a producing zone and diffuse at least partially throughout said liquid column.

2. A method of treating oil wells containing a column of corrosive formation liquids which comprises the addition thereto of a substantially oil-insoluble, water-dispersible, corrosion inhibiting composition having a specific gravity greater than 1.05, comprising a liquid iron corrosion inhibitor which has a specific gravity of less than 1 and a stable dispersion of an inorganic solid in oil wherein the diameter of the individual particles of said inorganic solid is less than 1 micron.

3. The method of claim 1 wherein the inorganic solid has a density within the range of about 1.4 to about 6.

4. The method of claim 1 wherein the iron corrosion inhibitor is sodium polydodecylbenzene sulfonate.

5. The method of claim 1 wherein the iron corrosion inhibitor is barium polydodecylbenzene sulfonate.

6. The method of claim 1 wherein the inorganic solid is sodium tripolyphosphate.

7. The method of claim 1 wherein the inorganic solid is barium oxide.

References Cited in the file of this patent UNITED STATES PATENTS 2,466,530 Blairet al. Apr. 5, 1949 2,501,731 Mertes m. Mar. 28, 1950 2,599,384 Gross et al June 3, 1952 2,671,757 Wisherd Mar. 9, 1954 2,728,727 Marsh Dec. 27, 1955 2,785,127 Shock et al. Mar. 12, 1957 

1. A METHOD OF TREATING OIL WELLS CONTAINING A COLUMN OF CORROSIVE FORMATION LIQUIDS WHICH COMPRISES THE ADDITION THERETO OF A WEIGHTED CORROSION INHIBITING COMPOSITION, SAID COMPOSITION COMPRISING A LIQUID IRON CORROSION INHIBITOR HAVING INCORPORATED THEREIN AS A WEIGHTING AGENT A STABLE DISPERSION OF AN INORGANIC SOLID IN OIL WHEREIN THE DIAMETER OF THE INDIVIDUAL PARTICLES OF SAID INORGANIC SOLID IS LESS THAN 1 MICRON IN AN AMOUNT SUFFICIENT TO INCREASE THE SPECIFIC GRAVITY OF THE INHIBITOR COMPOSITION ABOVE THAT OF THE CORROSIVE LIQUIDS TO ENABLE THE INHIBITOR COMPOSITION TO FALL READILY THROUGH THE LIQUID COLUME TO A PRODUCING ZONE AND DIFFUSE AT LEAST PARTIALLY THROUGHOUT SAID LIQUID COLUMN. 